1. Field of the Invention
The present invention relates to a solder ball supply device which can supply a large number of preliminary solder balls, which are used for fixing tip parts of surface-mount-type to substrates, to the substrates at one time.
2. Background Technology
Along with advance in technologies in recent years, ICs are highly integrated than ever and there is a tendency of increase in the number of input and output terminals on the ICs. These input and output terminals are also miniaturized due to miniaturization of IC chips. Such input and output terminals are fixed on the four corners of IC packages or provided on the back of the packages.
In the case of IC chips having input and output terminals on the back of a package, a number of plated through-holes are provided on the back. Preliminary solder is supplied to the plated through-holes to fix the input and output terminals to the circuit board by the solder to ensure conductivity between them.
One method of supplying solder to plated through-holes on the back of packages is printing a creamy solder by screen printing. Another method comprises taking solder balls out of a storage section using a vacuum pick-up instrument, dipping these solder balls in a flux, and supplying them to the circuit board (U.S. Pat. No. 5,088,639).
The screen printing involves solder-drawing, a phenomenon in which a viscous creamy solder is drawn when screen is peeled off. Because some projections produced by the creamy solder are too small or too large, it is difficult to constantly supply a prescribed amount of solder cream. If the projections are too large, the amount of the solder cream is large and this solder cream may contact the other creamy solder in the narrowly pitched input and output terminals. This may cause short circuit between electrodes.
On the other hand, because the method proposed by U.S. Pat. No. 5,088,639 retains solder balls in a storage section, solder balls may not be sufficiently adsorbed by the vacuum pick-up instrument, if the number of balls to be picked-up are large when these are taken out from the storage section.
In addition, because in this method the solder balls are dipped in a flux as they are adsorbed in the vacuum pick-up instrument, the flux may be adhered to adsorption nozzles of the vacuum pick-up instrument. This may cause malfunction in adsorption of solder balls, and requires frequent cleaning of vacuum pick-up instrument.
An object of the present invention is therefore to provide a solder supply method without these problems, particularly, a solder supply method by which a large number of solder balls can be certainly supplied without causing adhesion of flux to the vacuum pick-up instrument.